It's actually a pretty small patchset in reality, when you consider what it adds.

It's not in mainline for a few reasons:

1) Mainline is run mostly by people with little to no understanding of security, both in terms of the mechanics behind it, as well as the principals behind it. "A bug is a bug" won Linus a pwnie, and he deserves it. The upstream reaction to security issues is flawed and dumb.

2) Some of the patches can be arch-specific, and I guess Linus doesn't like that. example: PaX has had UDEREF for ages, but only with intel adding SMAP (they are essentially the same thing) does Linux support such a thing, because it's a standard in some piece of hardware, as opposed to using the hardware in some other non-official way. It's idiotic.

3) Brad has no intention of pushing for upstream. He doesn't like them, they don't like him, and it's obvious why - only one of them cares about security. It's been fairly blatant that Linus is abrasive, if you see him talk to PaX Team on some commits it is usually just a lot of back and forth cursing.